Reactive sputtering process

Abstract

In magnetron-type reactive sputtering the properties of the deposited layer are to remain constant throughout the entire use of a target, independey of the state of erosion, even after an exchange of targets. The method is also to be applicable for magnetron sputtering sources having a target consisting of several components with different partial discharge powers. Before sputtering of the substrates, the magnetic field strength associated with each partial target is set without reactive gas. Thereafter, a predetermined set of values of characteristic parameters is set by control of the reactive gas flow. During the subsequent sputtering the set of values predetermined for each partial target is kept constant by the controllable reactive gas flow. The first two steps are repeated at certain intervals in dependence of time the targets are used. Optical coatings or corrosion protection coatings may be fabricated by reactive sputtering in accordance with this method.

What is claimed is: 
     
       1. A method of reactively coating substrates with a magnetron sputtering source including partial targets composed of at least one component, a magnet system located behind each partial target, at least one controllable gas inlet, and a device that applies pulsed power into a plasma, the pulsed power having a period composed of a feed time and an intermission, the method comprising: (a) prior to coating of the substrate, changing at least one of a magnetic field strength associated with each partial target or the feed time of the pulsed power in an inert gas without reactive gas at a discharge pressure, wherein a set of values of parameters characteristic of non-reactive plasma is obtained;   (b) prior to coating the substrates in a constantly maintained magnetic field for the partial targets, changing discharge parameters by at least one of (i) admitting one of a reactive gas or a reactive gas and an inert gas, or (ii) changing the feed time of the pulsed power for the partial targets, wherein a set of values of parameters characteristic of reactive discharge predetermined for each partial target is obtained;   (c) during sputtering, maintaining constant the predetermined set of values of parameters characteristic of reactive discharge for each partial target for at least a fraction of a duration of use of the partial targets by at least one of (i) controlling one of gas flow or gas pressure at the controllable gas inlet, or (ii) controlling a feed time of the pulsed power;   (d) repeating (a) and (b) at predetermined intervals during use of the partial targets, and subsequently continuing to coat the substrates.   
     
     
       2. The method of claim 1, further comprising forming the set of values of parameters characteristic of the plasma discharge from a value triplet of discharge voltage, discharge current and power fed into the plasma measured over a length of the period. 
     
     
       3. The method of claim 1, further comprising forming the set of values of parameters characteristic of the plasma discharge from a pair of values of discharge voltage and one of an optically or electrically derived signal representing a state of the plasma. 
     
     
       4. The method of claim 1, further comprising forming the set of values of parameters characteristic of the plasma discharge from a pair of values of discharge power and one of an optically or electrically derived signal representing a state of the plasma. 
     
     
       5. The method of claim 1, further comprising forming the set of values of parameters characteristic of the plasma discharge from a pair of values of discharge current and one of an optically or electrically derived signal representing a state of the plasma. 
     
     
       6. The method of claim 1, further comprising determining the set of values of parameters characteristic of the plasma discharge in accordance with a state of erosion over the duration of use of the partial targets. 
     
     
       7. The method of claim 6, wherein the formed set of values are one of the same or different in (a) or (b). 
     
     
       8. The method of claim 1, wherein a length of the period is set in a range of several micro seconds to several seconds. 
     
     
       9. The method of claim 1, wherein during the feed time, the partial targets are discharge cathodes, and wherein the discharge burns in a direction of at least one additional electrode provided in the discharge chamber, which is set as an anode.   
     
     
       10. The method of claim 9, further comprising feeding power such that during a length of the intermission, the partial targets are low-ohmically connected to an anode potential such that the voltage between the partial targets and the anode does not exceed 15 V. 
     
     
       11. The method of claim 1, wherein, during a given period, the method further comprises setting some of the partial targets as cathodes and setting at least one of the partial targets as an anode, wherein, during the feed time of a next period, the method further comprises switching a partial target from a cathode to an anode and switching the at least one partial target from the anode to a cathode, and   wherein, for both pole directions, the method further comprises independently selecting feed times and power fed during the feed times.   
     
     
       12. The method of claim 11, wherein, during the periods, at least one additional electrode is set as an anode. 
     
     
       13. The method of claim 11, wherein during the periods, at least one additional electrode is set for an arbitrary electric potential. 
     
     
       14. The method of claim 1, further comprising determining an actual value of the supplied power used for controlling from multiplication of discharge voltage and discharge current, and forming an average value during a given period.   
     
     
       15. The method of claim 1, further comprising feeding one of the reactive gas or a reactive gas mixture into a discharge chamber adjacent to the partial targets. 
     
     
       16. The method of claim 1, further comprising igniting the discharge in inert gas without feeding of reactive gas; and automatically setting the operating point of the discharge by a reactive gas control loop.   
     
     
       17. The method of claim 1, further comprising igniting the discharge in a mixture of inert gas and reactive gas; and automatically setting the operating point of the discharge by a reactive gas control loop.   
     
     
       18. The method of claim 1, wherein during reactive sputtering, the method further comprises feeding power according to a constant power process; and setting a reactive gas flow by a reactive gas control loop, whereby one of a discharge voltage or a discharge current is stabilized at a predetermined value.   
     
     
       19. The method of claim 1, wherein during reactive sputtering, the method further comprises feeding power according to a constant power process; and setting a reactive gas flow by a reactive gas control loop, whereby one of a discharge power or a discharge current is stabilized at a predetermined value.   
     
     
       20. The method of claim 1, wherein during reactive sputtering, the method further comprises feeding power according to a constant current process; and setting a reactive gas flow by a reactive gas control loop, whereby one of a discharge voltage or a discharge power is stabilized at a predetermined value.   
     
     
       21. The method of claim 1, wherein, for some of the partial targets, reactive gas flow is maintained constant, and for other partial targets, the feed time of pulsed power is maintained constant, wherein the reactive gas flow and the feed time of pulsed power are maintained constant by several control loops on the basis of the predetermined set of values of the parameters characteristic of the reactive discharge predetermined for each partial target.